High concentration agar agar gel and combinations thereof



- June 2, 1936. H VQN BRANDT I v 2,042,917

,. HIGH CONCENTRATIO R-AGAR GEL A D Patented 2, 1936 I UNITED STATESPATENT OFFICE HIGH CONCENTRATION AGAR AGAR GEL AND COMBINATIONS THEREOFHenry von Brandt, New York, N. Y. Application July 22, 1932, Serial No.624,119 13 Claims. (Cl. 1847) This invention concerns a highconcentration time after the imprint has been taken so th t homogeneousagar agar gel as a base for an imtrue casts may be made therefrom. prinmaterial,and a method of making the Furthermore provisions have beenmade that earne -more particularly a material serving to the imprint maybe preserved, and may be reobtain a negative imprint of the shape of aplastic duced at a later date to the exact size which it body, be it asculpture, an art object, or a comhad at the time the imprint was taken,a simple mercial article, a fossil, or a live or dead organic processbeing required thus to Iii-condition th body. imprint.

This material finds a prominent use in the Provisions have also beenmade whereby it is arts and in the medical sciences, where a truepossible to preserve the exact dimensions, shape in replica of the humanbody or any part thereof, and detail of a fresh imprint for largerperiods like the ear or foot, is to be made. Thus for of time withoutwhole or partial losses due to instance, the dentist may use thematerial of shrinkage, bacterial growth, or mold; this is acmyinvention, where he desires to obtain an imcomplished by one single,lasting treatment.

print of the oral cavity, and in the following Another object of thisinvention has reference 15 exemplary descriptionIhave specific referenceto to hygiene. Throughout the whole manufacan adaptation of my inventionfor such purposes, turing process this imprint material or any partalthough it is understood, that the material as thereof does not requireth t h of human described as well as more or less concentrated mayhands. The product is sterile, and until the very 0 serve in ramifleduses. time of actual use I preserve the material in its 20 The grade ofconcentration as well as the original sterile condition. grade ofconsistency depend largely upon the A further object of this inventionis to create nature of the object of which an imprint is to an imprintmaterial oi whiteor very lightbe taken. For instance, if a true replicaof the color, which may be colored to any desired shade.

dental cavities of a jaw are desired-which case It is a very importantobject of this invention, 25 the dental tray filled with the imprintmaterial and one which largely influences the choice of may have to beturned upside-down in order to the ingredients, that the material, afteran imbe applied-the imprint material should be more print has beentaken, may be exposed to any concentrated and denser than for taking adeli atmosphere without putrefaction or molding.

3 cate imprint, of hair and the like, for instance. It is also an objectof this invention to allow One object of this invention is to prepare anclose control of the setting speed and temperaimprint material, whichsets quickly while the hir i p nt s being taken, said imprint materialIt is further understood that a material of showing however Suflicient rs e y after the this kind must comprise a binder which holds it t 8 thatit y be removed from the together, so that it does not readily breakapart;

or in l. r in n iaw. w h shows n rat the same time the material shouldnot be cuttings as in dental cavities, the resilient parts mucilaginousto the extent of adhering to the 0f the mater a being temporarilyStretched articles of which an imprint is to be taken; I

ing removal, While slipping aw y from Su have reached the object ofobviating the coverundercuttings. ing of the article of which an imprintis to be It is however understood that the material taken with a coat ofmaterial which prevents admust resume exactly the same shape it hadhesion of the imprint material to said article. On before, after havingbeen withdrawn over th the other hand the material is to show thegreatest protruding parts and must then retain its shape DOSSIbleCoheslonand size. In other words, it must be truly elastic In orderttootftam these vanous and and resilient and should not remain distorted.Others" winch be furuller understood i Another object of this inventionis to prepare the folowmg' I have not on y brought about an imprintmaterial in such a manner that it provements as to the ingredients usedin my material, but I have also developed special and eco may bepreserved mdefinitely' and so that only nomical processes of preparingthe material, and 50 a short Process is required to place It f thebinder used therein a method of preserving the dition take an imprintWhenever deslredimprint material and of conditioning it for use.

A further object of this invention is to provide The binder used inpreparin'g t material is an imprin m t ri whi h p rv its xact of utmostimportance. Gelatinous jellies, the shape and dimensions for areasonable length of consistency of which should be as high as possible,

are desirable, and I have found that class of such material, whichbroadly falls under the term of agar agar, the most suitablebinder,provided a highly concentrated homogeneous aqueous mixture thereof canbe prepared, which does not form lumps.

In the prior art commercial agar agarcould not be liquefied in aqueoussolution without forming lumps at a higher concentration than at anapproximate agar-water ratio of 1:20.

The major object of my invention is to condition commercial agar agar insuch a way that it forms a homogeneous, cohesive mixture with water at aconsiderably higher concentration than that mentioned above or knownheretofore.

This is attained by freezing the commercial agar agar after it has beenmixed with the water, or otherwise changing or destroying the cellstructure thereof and releasing the readily soluble gelosine. In thismanner I have obtained a homogeneous binder, which contains agar agarand water in a ratio of up to 1:6.

This novel agar solution provides a basis for many other compounds whichrequire ahigh concentration of agar agar.

Such a high concentration may also be obtained by exposing the mixtureto ultra-violet rays, which destroys the cellular structure of agaragar, releasing the gelosin.

As a. body for a molding compound of this kind organic materials andargillaceous earth have been used most commonly heretofore. I have foundthe predominant use of such materials for the purpose of giving body toan imprint material to be incompatible with the objects which werementioned above; they do not furnish a lasting material, allowingputrefaction, contraction and molding; they crack when dried: most ofthem cannot be restored to their original shape; and theywill,--particularly argillaceous earth, bentonites, and fuller'searth,absorb and retain air, to an extent where the negative casts madefrom such a material, are of an inferior quality.

The object of providing a body substance which is not subject to suchshort-comings has been attained by using as a major part of the body asubstantially insoluble virgin rock which in itself provides for a morecompact structure; still, a minor part of the body may be made up of afiller such as clays, diatomaceous-earth, fossil earth, argillaceousearth, and the like so that a material of denser structure is obtained.But the proportionate contents of the organic material or of suchmaterials that are partly organic, are in all instances restricted to aminor proportion of the ingredients of the body, so that theirdisadvantages do not prevail.

The following exemplary formula may be used for explaining a simple andeconomic way in which this imprint material may be prepared:

Binder Parts Powdered dry agar 24 Distilled water U. S. P. glycerine 18Body Powdered dry soapstone (rock) 34 Powdered dry zinc oxide 17Powdered dry silica (rock) 32 Pulverized dry clays 2O 15 parts E. Ballclay 5 parts molding clay All ingredients of body and binder arecomputed by weight".

The zinc oxide, commercial or natural (zincite) serves as a cohesiveagent as well as for the purpose of closing the pores of the finishedmaterial. As coloring agent Fe-iOa was used. The choice of coloringmatter is of course arbitrary.

There are several ways to prepare this imprint material, but one of themI consider highly suitable, hygienic and economical:

(1) The liquid ingredients (water, glycerine) should be mixed at roomtemperature;

(2) All dry and pulverized ingredients such as commercial agar agar,stone, clays, zinc oxide (if 'desired, also asbestos fiber) should beweighed sure of live steam.

pressure rises above afore-mentioned limits, the

and mixed thoroughly with each other;

(3) Under constant but slow stirring the thoroughly mixed dryingredients are added to the liquid (water-glycerine-solution), until ahomogeneous batter has formed. Special care should be taken that no airis introduced into this batter (while and after mixing) that will happenif the stirring device rotates too fast.

(4) This homogeneous batter should be frozen in any one of therapid-acting commercial freezers (using crushed dry-ice combined withether, or the like). The freezing should continue even after all of thebatter seems to be frozen stiff in order to assure the mutilation ordestruction of substantially all agar agar cells.

(5) The frozen batter is melted and under constant slow stirringgradually heated up to the point where the agar agar mixture will beingto liquefy,and there the heating should be discontinued. (This pointvaries with the kinds of agar employed, but will be in the neighborhoodof from 40 to 70 centigrades) This warm batter is filled intocontainers, preferably of the design referred to hereinafter. Afterintroducing the batter in these containers, the latter may be sealedpermanently as the further steps of the process do not require directhandling of the material. (Under certain circumstances the frozen andre-melted batter may be introduced into the containers without previousheating, although care must be taken not to bring free air into thecontainers as this may have a detrimental eil'ect upon the contentstherein).

(6) The containers with the material are then placed into an autoclave.This name is commonly applied to a machine much used in industrialplants for the purpose of subjecting materials to heat and pressure.Here the material is subjected for 60 minutes to a heat of 250Fahrenheit (121 centrigrade) and to not more than 15 lbs. pres- (If theheat and the steam characteristic quality of re-jellification of theagar agar will gradually decrease until, at a certain temperature orpressure (20 lbs.) the agar agar will cease to gelatinize). During thisheating process certain important changes will 6 take place in thematerial: (a) the agar agar will liquefy and combine with thewater-glycerine mixture, forming later,-when cooled-,the desired highlyconcentrated agar-jelly; (b) the liquid agar solution will be evenlydistributed throughout the whole batter inside the container, forming afine network of agar-channels between the multi-shaped solid particlesof the mixture, and I obtain a substantially homogeneous mass,- theimprint material; (0) incidentally allbacteria and spores, which mighthavebeen' introduced into the mixture, will be destroyed-leaving thematerial absolutely sterile until the container is opened for thepurpose of using the contents for making an imprint.

Another way to manufacture terial would be the following:-

The powdered dry agar agar is mixed thoroughly with the water until astifi batter is formed in which all agar-particles have come into directcontact with the liquid. Then this batter is frozen as quickly aspossible in order to prevent loss of water by evaporation. The freezingprocess should be continued until the greenish-gray color of theagar-agar batter temporarily turns white.

Precaution should be taken that the freezing fluid does not come intodirect contact with the batter as this will prevent in most casesre-jellification, and moreover, when ether contacts with the agar agarit confers upon the latter a nauseating odor and unpleasant taste.

The freezing process should be continued until the agar agar batter isthoroughly frozen and its color has changed temporarily to white. Thefrozen cake of agar is then removed from the freezer, placed into aheating vessel equipped with a slowly rotating stirring device, andcovered with so much glycerine as the ultimate use of the material maywarrant. This treatment serves twofold: First, while the frozen agar ismelting the layer of glycerine prevents loss of water by evaporation;second, due to the slow melting of the frozen agar and the constantstirring, the glycerine will be thoroughly and finely distributedthroughout the whole agar solution. Direct application of heat up to theboiling point will finally yield a highly concentrated homogeneous agarsolution of the afore-mentioned ratio.

This novel agar solution furnishes a basis for many compounds whichrequire a high concentration of agar agar.

From this stage I proceed as follows to obtain the imprint material:

The frozen agar agar, as it was covered with glycerine, is melted,heated under constant stirring, and likewise under constant stirring thedry and powdered ingredients are added until thoroughly mixed with theagar-water-glycerine mixture, forming a stiff batter of highconsistency, the heating temperature is raised up to centigrade, andkept at the boiling point for a short period.

The mixture is now filled into containers and sealed.

There is another method whereby the highly concentrated agar solutionmay be obtained:

Again the dry agar agar and water are thoroughly mixed and thenirradiated with ultraviolet rays. Such ultraviolet treatment willdestroy the cellular structure lower the absorption capacity of agaragar to considerable extent and by releasing the soluble gelosin lowerthe dissolving temperature of agar agar to about 40 centigrade,permitting thereby much higher concentration than heretofore has beenpossible. Due to the fact that certain agar agars are less re sistant toultra-violet rays than others, the irradiation periodshould,-general1y,-not exceed 30 minutes. Excessive irradiation mayresult in partial or complete loss of the agar agars characteristicquality of being liquefied and solidified repeatedly, withoutdetrimental influences. After treatment of the agar agar withultra-violet rays an imprint material is prepared exactly as describedin a connection with the previously described processes after freezingand thawing.

In order to increase the cohesion in such concentrated agar agarsolutions commercial or the imprint manatural zinc oxide (zincite) (upto 15% of the body-forming ingredients) may be added to and incorporatedin the mixture in finest distribution.

To increase elasticity and likewise to absorb surplus water, non-frozenpowdered dry agar agar may be added additionally in small quantities (upto 2%). The tiny cells of the agar agar possess high absorption power(about 20 times their dry-weight) and besides are valuable for thereconstruction of the dried-out and shrunk materials to their formeroriginal dimensions and shape.

In accordance with the intended use of the material, certainmodifications of the basic formula may be brought about, which may beguided by the following considerations:

The necessary concentration of agar agar may be reduced by substitutingsubstances of. more tenacious and mucilaginous character such as gelatin(glue of bones), Mouss de Chine, Layor Caranga, algae of the rhodohyceae-specie, or isinglass and the like, resulting in an imprintmaterial of high viscosity but slower setting speed.

An increase of the glycerine oontents,with or without a proportionatedecrease in water,- will give a fatty, slow-drying material, which, whenair dried possesses leather-like appearance of rather tough andtenacious character-but the material will also mold more readily.

Increasing the silica-rock and decreasing the clay contents, will resultin a more porous and faster drying material, but it is also apt to crackwhile a cast dries.

Replacing part or the whole of the natural rock ingredients in themixture by commercially improved silica such as calcined diatomaceoussilica or calcined fossil silica will result in a material of extremelylight weight as may be desired for taking delicate imprints of suchobjects as hair.

A suitable formula is:

Binder Parts Dry powdered agar agar 20. Distilled water Glycerine 10Body Silica ash 30 Powdered S102 R Zinc oxide 20 South Carolina clay 10Generally, the calcined silica may be added in a quantity sufficient toimpose upon the imprint material a characteristic compactness, lightnessand yieldability, lightness in color too, unless 011'- set by coloringingredients. In the foregoing the SiOz and clay may also be replaced bycalcined silica also termed silica ash.

For purposes of this invention calcined silica should therefore beclassified as a rock".

An introduction of asbestos fiber into the material will providestructure and tensile strength in the compound as a whole, but not morethan 3% of the entire weight of ingredients in the imprint materialshould be added. Long fibers have a tendency to coil up" in the mixtureforming annoying lumps, and likewise may impair the detail of theimprint. In order to increase the tensile strength it is. advisable touse raw,

crude asbestos fiber in preference to commercially improved fiber.

If material of less consistency is desired, the agar water proportionmay be stretched, although the glycerine should be increased inproportion;

due to the'lessenedv amount of the agar binder in such a materialanother cohesion-increasing agent should be introduced in the materialto make up for the loss in binding power.

Exceedingly fine-grained clays produce sharper imprints, but may lose indetail if immersed in cold water and may also color the saliva-if usedfor dental purposes.

Darker clays are more fatty, than light-colored ones; the former willordinarily retain water and moisture longenthan the latter, but they dryslower and invite bacterial growth.

Bentonite clays absorb about 12 times their weight in water and increasein volume considerably while doing so, but upon drying they shrinkextremely and crack the cast due to their ab- "normal shrinkage;besides, bentonites have a tendency to absorb and retain air, which maygive the material large voids and a sponge-like appearance, which isvery annoying if detail is wanted. a v

The term agar agar is used here to describe certain material which hascertain physical characteristics. The derivates of agar agar, gelose forinstance or any. other equivalent compound may be substituted wholly orpartly for the agar agar.

Agar agar is very sensitive to acids, and in the choice of rocks, earth,and organic material, care should be taken that such material is notacidic.

In order to illustrate modifications, for in-- .stance for the purposeof introducing a higher silica content, I also give the followingexemplary formula:

Binder Parts Powdered dry agar 23 Distilled water .1. 140 U. S. P.glycezine 1o Powdered 810i". 60 Powdered soapstone 24 Dry South Carolinaclay; 22 -.z1'n nxidn I 16 I may go to the polnt of eliminatingargillaceous earth and clays altogether; in which instance thefollowin'g exemplary formula may be adhered to in preparing my materialas described Proceeding .in accordance with the second manufacturingniethod described above, the material is substantially finished, when itis placed into a container and sealed therein; any type of a closure. acan for instance, which can be sealed or closed air tight, is suitable.

, But in the first method referred to, the material is subjectedto-further treatments after hav- ,ing been sealed in the container, and,since these comprise heat and pressure treatments in which the materialchanges in volume, and since it is not advisableto allow the amount ofair necessary for a cushion inthecontainer, the .contair 1 er should becollapsible and readily allow propagation of pressure andheat'therethrough and throughout the contents. Therefore I prefer theuse of a flattened container, made of thin-sheet metal or other'ylel'dable material.

Such a container is illustratedin the accompanying drawing, in which:

Fig. 1 shows a perspective view of the closed container;

Fig. 2 shows a. longitudinal section thereof. Fig. 3 is a cross-section.

In the drawing, the collapsible tube His the flat body of the container;the ends l2 are folded over, and sealed and the container is filled withthe material.

These metal containers are filled with the imprint ,material,not to theamount they could receive when shaped cylindrically, but to theircapacity in the fiat condition shown,closed and sealed permanently.Turning the ends of the collapsible tube over fiat, will also allow forexpansion during heat treatments. In this state, the metal containersand the material therein enclosed are subjected to the heat and pressurespecified above.

The material, in a sealed container of the type shown, may be keptindefinitely. When to be used, its temperature is raised to about 60centigrade in boiling water, whereupon one end of the container isclipped off and the material squeezed out of the container and then usedto take the imprint. Itwill set in one or two minutes (according to itsconsistency and ingredients) and their the imprint may be withand then,in the period of days according to climatic conditions willshrink as itloses moisture. A shrunken, and dried out, imprint may be reproduced totrue imprint size at any time by being soaked in plain water or in waterwith a trace of glycerine. This soaking should extend from a few minutesup to about 24 hours,-depending upon the grade of desiccation of thecast.

Freshly made imprints may be preserved for days and weeks in their exactshapeand size,

- without shrinkage, by keeping them in an airtight container, such as aglass jar with fitted-in stopper. A few drops of distilled water keepsthe air moist inside of this container, and a drop of phenol,formaldehyde (formalin) or the like should be added to prevent bacterialgrowth.

Although I have shown and described one form of embodiment of myinvention in detail, yet I do not wish to be limited thereby, except asthe state of the art and the appended claims may require, for it isobvious that various modifications and changes may be made in the form tof embodimentof my invention, without departing from the spirit andscope thereof.

What I claim is:--

1. An imprint material comprising a highly concentrated homogeneousgelatinous binder, a

. body of powdered material and a mixture of hard and soft virgin rockforming the major part of said body material.

2. In an imprint material a homogeneous gelatinous binder comprisingagar agar and water, at a ratio exceeding 1 to 7.

3. The method of preparing a homogeneous binder of an imprint materialcontaining a high concentration of agar agar in water, comprising mixingagar agar into water, irradiating said mixture with ultra-violet rays,and heating it until it forms av gel.

4. The method of preparing an imprint material with an agar agar binderand a mineral body, comprising rapidly freezing an agaragarwater-glycerine batter, and boiling said solution with a mineralbody in powdered form.

5. An agar agar solution characterized by a high concentration of agaragar and water, said solution being a homogeneous gel containing agaragar and water of substantially the ratio 1 part agar agar to 6 parts ofwater and'obtained by heating a non-gelatinous mixture of agar agar andwater, after the cellular structure of the agar agar in said mixture hasbeen broken up so that the gelosin in the cells is set free.

6. A highly concentrated agar agar solution obtained by rapidly freezinga substantially nongelatinous mixture oi agar agar and water, and laterheating said mixture to the point where the agar agar dissolves.

7. An agar agar solution, characterized by a concentration of agar agarin water in excess of a proportion of 1:7, prepared by rapidly freezinga substantially non-gelatinous agar agar-water mixture, and then heatingsaid mixture to the point where the agar agar dissolves.

8. The method of preparing an imprint material, comprising mixing abatter of agar agar and cold water in high concentration. irradiatingsaid mixture with ultra-violet rays for a predetermined period, heatingthe mixture until it dissolves, and adding a powdered body materialthereto.

9. A substantially non-shrinking imprint material comprising aconcentrated agar agar water gel 01' the type described in claim 5 andpowdered rock.

10. In an imprint material a binder comprisinga viscous homogeneousmixture containing agar agar and water substantially in the ratio 01' 1part agar agar to approximately 6 parts by weight of water.

11. The method of preparing a homogeneous binder for an imprint materialcontaining a highly concentrated emulsion of agar agar in water,comprising mixing agar agar and cold water, rapidly freezing themixture, and heating said mixture to the point where the agar agardissolves.

12. The method of terial, comprising the preparation of a cold mixtureof commercial agar agar, water, and the required mineral substances,freezing said mix-- ture, melting said frozen mixture and heating ituntil a highly concentrated paste is obtained.

13. A highly concentrated agar agar solution prepared from a frozennon-gelatinous substan tially 1:6 mixture 01' agar agar and water.

HENRY VON BRANDT.

preparing an imprint ma-

